I'm using Sennheiser 555, and I hear hiss at all times (save when it gets drowned by the music). To ensure I get no suggestions to adjust my volume settings in Windows and such, I simply disconnected the USB cable, so the amp has no input. The hiss is still there, and gets louder as I turn up the volume knob. So it seems to be generated by the amp. The hiss is not very loud, but even with the volume at zero I don't have to struggle to hear it. I'm on 230V, if it matters.

Since this was supposed to be an upgrade, I'm feeling a bit down. I mean, I know low quality amplifiers have noisy backgrounds, but from what I read about Zero I had hoped I'll get a decently silent background. I get no hiss with 555 connected directly to Soundblaster X-Fi. I don't know that much about audio, except that maybe higher impendance headphones might help (555 is 50 ohm). Or not, since I would have to turn up the volume and hiss also increases then?

It is quite long time since i completely upgraded my ZERO (upgrade included replacement of headphone amplifier with another one with silent background), but I don't remember me complaining about background noise (with AKG K240).

I would say that this is not normal (original headphone amplifier is quite nousy, but nothing horrible), but it depends on how loud are you listening (with K240 a was listening with potentiometer at 8 to 9 o'clock).

You can try LINE OUT with another amplifier to chceck if headphone amplifier is really the problem.

I also have the volume quite low, definitely lower than 9 o'clock. Probably around 8 (can't look right now since I'm not at home). I don't have other amplifiers yet - this is my first one.

Btw, I'm using USB because on S/PDIF Zero would loudly click (from within its housing, not in the headphones) every time the signal started / stopped. Even worse, after a couple more seconds I would always get a relatively loud pop in headphones, so it was unnerving, every time a song ended to wait for the dreaded pop. The pop was probably caused by the mobo (with built-in Realtek), not Zero.

I tried to connect Zero to other power outlets, guessing it might change the noise, but to no avail. So it's again on my UPS-protected chain.

Anyway, Zero sounds nice otherwise, its just this "shhhhhhhhhhh"... even when the music drowns it, of course it's still there, reducing the total clarity...

One other thing bothers me: when turning Zero on/off the headphones receive a loud pop as well. Hopefully it isn't detrimental to the headphones?

I'm new around here, what would be the best way to ask for recommendations on affordable (sub $500 if possible) dac+amp with a neutral sound and as-quiet-as-possible background? Or at least amp, I can have Zero as a DAC, although it will be a pain to switch two devices all the time.

Click (relay inside ZERO) when using S/PDIF is not problem of ZERO and it is caused by S/PDIF source. Some "not good" sources turns the S/PDIF output off for a while even between tracks (when changing track with optical S/PDIF you can see that red light disappers for a while).

Don't take this as recommendation, but only as my experience: I upgraded few ZEROs to version "amarok", all of them were OK when in original state.

After this upgrades the sound of DAC changed to more neutral, less harsh highs, better soundstage and better defined basses. New AMP section can't be compared to the old one - way less distortion, better channel separation and noise below noise of DAC section (new AMP is silent with K240 even at full volume).

One owner of uprgraded ZERO told me that it is superior to Icon HDP, Fubar IV or Yulong DAH1. Another owner compared it to HS-DAC (DIY DAC comparable to H/K HD990).

Well, you certanly got me interested, but... the most electronics I can handle is putting computers together (which is about as simple as it gets ). I took a look at your website, and this mod is way out of my league.

You know, I never understood one thing... why can't some company like TianYun take good advice like this and improve the device in several mayor revisions. And in the end, get a very cost-efficient product with performance that rivals the best of them.

Then again, 3TB harddrives are also sold at 2x the price of 2TB harddrives, even though the components hardly cost more

it will be just short. I decided to buy DAC. I flipped through some reviews and ended here in this thread (sorry I didn't scan all the 616 pages...). I hate how Zero looks but I will leave the aesthetics behind and buy it:)

ZERO 09 with USB and OPA627 is the best choice under 300$ (or maybe 500$) when properly modded.

Original ZERO is surely better than fubar.

My experience with OPA627 in ZERO is very good - resistance between pin1 a pin5 was 55k like in original, offset was little lower than typical from datasheet ... so I can say, that it is original OPA627 ... or very good fake. :)

my Zero is safe and sound sitting on my desk and I am in the process of the sound testing. The first impression is it needs to be burned-in (for those who believe something like this actually exists ) but I am not in no way disappointed with it. Actually it plays very nice and I am so far quite happy about even the headphone input which can be improved somehow which I will definitely do later with the help of one member here.

Just now I would like to ask a very "dumb" question. Now I have an on-board (Gigabyte) sound card in my computer which is connected to Zero with an optical cable. I use Foobar2000 player along with Asio4All driver with "Always resample 44.1kHz <-> 48kHz" enabled. DO I IMPROVE the sound output (the sound which gets from PC to Zero) when buying non-integrated sound card (for example ASUS Xonar DG) OR is it pointless and the digital sound is converted in Zero independently on what the source is (I mostly play FLACs and the source i mean Sample Rate and Resolution...). Say it another way... is it worthwhile to invest to a sound card when I use optical out and NEVER NOTHING else?

I wanna add that I use Zero as a Headphone amp and also as a DAC to my Amplifier (direct out via RCA).

Btw, I'm using USB because on S/PDIF Zero would loudly click (from within its housing, not in the headphones) every time the signal started / stopped. Even worse, after a couple more seconds I would always get a relatively loud pop in headphones, so it was unnerving, every time a song ended to wait for the dreaded pop. The pop was probably caused by the mobo (with built-in Realtek), not Zero.

At first I thought it must be the lousy motherboard integrated soundcard. Now, after two other DAC/AMP combinations found themselves on my table, I can confirm there is absolutely no pop whatsoever with them connected to the same source. The problem is ZERO.

Optical in is therefore useless on mine. Cannot stand that pop. It could be a bad sample? Can someone else please check, if you connect your (unmodified?) version 09 ZERO with toslink, is there any pop in your headphones a couple of seconds after the song ends?

Didn't try line out, I'll look around if I have something. But I won't use it in either case. I don't think I have any other S/PDIF devices. Will check with relatives - if someone has, I could at least try their computer cause they most likely have S/PDIF. Another computer is also the best test, as that's the source of my choice.